The well known agricultural practice of forage harvesting consists of cutting either green or mature crop material into discrete particles, and conveying the particles from the field to a storage facility, such as a silo. While in storage the crop material undergoes an acid fermentation to give the particles an agreeable flavor and to prevent spoilage. This overall operation, which is commonly referred to as an ensilage process, converts standing crop in the field to livestock feed, generally called silage.
An essential piece of farm machinery used for producing silage is the forage harvester which is adapted to gather standing or windrowed crop material from the field, chop it into small particles and then convey the cut crop material to a temporary storage receptacle, such as a wagon. Harvesters of this type are either self propelled or pulled by a tractor. Typically, forage harvesters comprise a base unit having a rotary cutter having a generally cylindrical configuration with knives peripherally mounted to cooperate with a stationary shear bar for cutting material by a shearing action as it is passed across the surface of the bar. The chopped crop material is then discharged from the harvester through a spout which directs the flow of crop material to a wagon towed behind or along side the harvester. U.S. Pat. No. 4,223,846, issued Sept. 23, 1980 in the name of E. H. Priepke et al, shows a self propelled forage harvester that has a general configuration that is typical of prior art base units.
Forage harvesters, regardless of the type, i.e., both self propelled or pull type, have a crop gathering attachment that initially encounters crop material, as the harvester moves across the field. As mentioned above, the crop being harvested is either standing, such as row crops, or windrowed. In the case of windrowed crop, a pickup attachment, extending from the front of the harvester, typically includes a reel consisting of a plurality of fingers, each of which is moveable through a predetermined path for engaging and picking up the windrowed crop material from the ground. The fingers urge the crop material rearwardly over side-by-side stripper plates that define slots through which the fingers extend. The stripper plates terminate in the general vicinity of a transverse auger that consolidates the crop material and feeds it through a rear opening in the header to the base unit of the harvester for processing. A typical forage harvester windrow pickup attachment is shown in U.S. Pat. No. 4,495,756, issued on Jan. 29, 1985 in the name of J. G. Greiner, et al, hereby incorporated by reference.
Prior art pickup attachments have been either rigidly attached to the base unit or have been pivotally mounted to allow lateral floating action. Lateral floating has an increasingly greater importance as attachments with increasing widths become more prevalent, because the wider attachments are more susceptible to changes in the ground contour. A change in such contour could result in one end of a rigidly mounted pickup being raised above the windrow material in the field over which it is being operated. This causes the crop to be bypassed, leading to inefficient operation. A header provided with the capability to laterally float, and thereby follow the ground contour, enables the header to be more effective over a wider area, resulting in improved operation by reducing losses. An example of a prior art forage harvester attachment with lateral float capabilities is shown in IDASS brochure, dated November, 1994.